IDPR Urges Caution As Avalanche Danger Increases

Published online: Jan 19, 2012News

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Avalanche
danger has been moderate to considerable in many Idaho locations with the little snowpack
that currently exists. The Idaho Department of Parks and Recreation (IDPR)
urges snowmobilers and backcountry skiers to use caution as they head out to
play. Incoming precipitation will likely increase the instability that
currently exists by adding additional stress to a faceted snow base.

"Anyone
heading outdoors to recreate in the fresh snow needs to take special
precaution," Rich Gummersall, Outdoor Education Coordinator for IDPR, said.
"What exists out there currently is a base layer with no bonding properties
with an ice layer sitting on top due to warming and rain showers. The incoming
precipitation will add additional weight, which will increase the stress on the
snow pack. The fresh snow will be deceiving and the perfect composition for
avalanches."

IDPR
encourages you to know the capabilities of yourself and your equipment and
familiarize yourself with terrain, snow and weather conditions. They also
encourage people to carry and know how to use proper rescue gear, take an
avalanche awareness course and visit avalanche.org for
current forecasts.

To
avoid being caught in avalanche terrain, you could avoid it all together or
roll the dice and hope for the best. However, you can also learn about
avalanches, which helps minimize your risk.

Most
large avalanche paths are obvious: an open slope, bowl or gully above timberline
that leads to a swath through the trees. However, small avalanche paths in the trees
can be just as dangerous. Slope angle is the most important factor, so you
should carry a slope meter. You also need to observe snow deposition patterns
and the effects of anchors such as rocks or trees that might prevent avalanches
on some slopes. Finally, bent or damaged trees are good clues that show where
avalanches have run in the past.

You
can receive avalanche training from the Idaho Department of Parks and Recreation.
There are also several avalanche centers where you can be trained: Sawtooth
Avalanche Center, PayetteAvalancheCenter
and PanhandleAvalancheCenter.

Avalanches
are caused by a steep slope, unstable snow and a trigger. An avalanche occurs
when the stress (from gravity) trying to pull the snow downhill exceeds the
strength (from bonds between snow grains) of the snow cover. The trigger for an
avalanche can be human, animal or weather. As recreationists, we need to ready,
willing and able to make safe travel decisions.

Avalanches
only happen when the slope is steep enough. Generally slab avalanches can occur
between 25 and 60 degrees, but most slab avalanches occur with starting zones
between 30 and 45 degrees. Above 60 or below 25 degrees, the stresses on the
pack from gravity typically are not enough to cause the snow to slide. The same
is true above snow sluffs.

Avalanches
only happen when snow conditions are unstable. When the snow cover is very
unstable, nature often broadcasts clear danger signs. Fresh avalanches are the
best clue. Snow that cracks, collapses or makes hollow sounds is also unstable.
Weak layers that are found by digging snow pits are signs of unstable snow.
Snow that has become wet from thaw or rain can also be dangerous. Even if you
find no signs of unstable snow, you should always travel using the techniques
listed above to minimize risk.

In
order to travel safely, you try and stay updated with recent snowpack stability
information. Since conditions in the backcountry can change daily, even hourly,
it is important that you also make your own assessment for any given slope.
Avalanche centers can provide you with information about previous snow and wind
events, buried weak layers and general concerns. So, be sure to visit www.avalanche.org.

In
addition, every snowmobiler and backcountry recreationist should carry a pack
with three days emergency supplies, a probe, shovel and an avalanche
transceiver (beacon). Most importantly, they should be comfortable using their
rescue gear.

You
can reliably avoid avalanches by recognizing and avoiding avalanche terrain.
Travel at the valley floor away from large avalanche run outs, along ridge tops
above avalanche paths, in dense timber or on slopes of 25 degrees or less that
do not have steeper slopes above them. Avoid cornices on ridge tops.

You
cannot entirely eliminate risk if you travel in avalanche terrain, but you can
minimize risk by using good technique, such as: climb, descend or cross avalanche
areas one at a time; cross a slope at the very top or bottom if possible; climb
or descend the edge of a slope rather than the center; carry and know how to
use avalanche rescue gear and turn back or alter your route if you detect signs
of unstable snow.

Over
the last five years, there have been 13 avalanche incidents in Idaho, 11 of which were
snowmobilers. Nationally, over the last five years there have been 83
snowmobile and 39 skier fatalities. 85 percent of avalanche victims will
survive if recovered within 15 minutes and 25 percent of avalanche victims die
of trauma incurred during the slide.

Surviving
avalanches can depend on luck; therefore, it is always better to avoid them in
the first place. Only 1 of 3 victims buried without a beacon survives. If you
are caught, first try to escape to the side or grab a tree or rock. Swim with
the avalanche to try to stay on top and avoid trees. When the avalanche slows
down, reach the surface or make an air pocket.

The
avalanche danger increases with major snowstorms and periods of thaw. About
2,300 avalanches are reported to the AvalancheCenter in an average
winter. More than 80 percent of these fall during or just after large
snowstorms. The most avalanche-prone months are, in order, February, March and
January. Avalanches caused by thaw occur most often in April.

Almost
all avalanches occur on slopes between 35 and 45 degrees. Slopes less than 30
degrees seldom produce avalanches and slopes steeper than about 50 degrees
sluff, so they often do not build up into slabs. It's the intermediate slope
steepness that produces most of the avalanches. The bad news is that the kind
of slopes we like to ski, snowboard or snowmobile usually produces most of the
avalanches. A black diamond slope at a ski resort is usually around 35 degrees-prime
steepness for producing avalanches.